I can easily spend over $100 on hinges alone. Picking the door up is another c-note. The hardware rarely lines up, figure at least another hour. Locksets can run from $12 - $600 + install. If it's an older home, many times the door may have to be shaped to fit, add another 1-2 hrs.
My average exterior door replacement runs about $500 for a frame home. You can pretty much double that for a CBS home.